R21xx-HP FlexFabric 11900 Layer 2 LAN Switching Configuration Guide

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• Dynamic entries—Dynamic entries can be manually configured or dynamically learned in order to
forward frames with a specific destination MAC address out of their associated interfaces and
might age out.
• Blackhole entries—Blackhole entries are manually configured and never age out. Blackhole entries
are configured for filtering out frames with a specific source or destination MAC address. For
example, to block all frames destined for a specific user for security concerns, you can configure the
MAC address of this user as a blackhole MAC address entry.
• Multiport unicast entries—Multiport unicast entries are manually added in order to send frames
with a specific destination MAC address out of multiple ports and never age out.
A static, blackhole, or multiport unicast MAC address entry can overwrite a dynamic MAC address entry,
but not vice versa.
To adapt to network changes and prevent inactive entries from occupying table space, the system uses an
aging mechanism for dynamic MAC address entries. Each time a dynamic MAC address entry is learned
or created, an aging time starts. If the entry has not updated when the aging timer expires, the device
deletes the entry. If the entry has updated before the aging timer expires, the aging timer restarts.
MAC address table-based frame forwarding
When forwarding a frame, the device adopts one of the following forwarding modes based on the MAC
address table:
• Unicast mode—If an entry is available for the destination MAC address, the device forwards the
frame out of the outgoing interface indicated by the MAC address entry.
• Broadcast mode—If the device receives a frame with an all-ones destination address, or no entry is
available for the destination MAC address, the device broadcasts the frame to all the interfaces
belonging to the corresponding VLAN except the receiving interface.
Configuring the MAC address table
The configuration tasks discussed in the following sections are all optional and can be performed in any
order.
The MAC address table can contain only Layer 2 Ethernet interfaces and Layer 2 aggregate interfaces.
This document covers only the configuration of unicast MAC address entries, including static, dynamic,
blackhole, and multiport unicast MAC address entries. For information about configuring static multicast
MAC address entries, see IP Multicast Configuration Guide. For information about MAC address table
configuration in VPLS, see MPLS Configuration Guide.
Configuring MAC address entries
Configuration guidelines
• A manually configured static MAC address entry has higher priority than an automatically learned
one. If a packet with such a source MAC address enters the device on a different interface from that
in the static MAC address entry, it is dropped.
• A manually configured multiport unicast MAC address entry has higher priority than an
automatically learned one. If a packet with such a source MAC address enters the device, it is
dropped.